James E. Lentz, president of Toyota in the United States, leaves a hearing on Toyota recalls on Capitol Hill in Washington on Tuesday. (Alex Brandon/Associated Press)

Toyota's U.S. president said the company's massive recalls might "not totally" solve the company's problems with unintended acceleration of some of its most popular cars and trucks.

Facing tough questioning Tuesday as congressional hearings began in Washington into a series of safety issues and the automaker's response to them, James Lentz defended the company's actions while acknowledging that the problems are far from over.

In a prepared statement, Lentz admitted that Toyota was slow to "come to grips with a rare but serious set of safety issues.

An emotional Rhonda Smith of Sevierville, Tenn., testifies on Capitol Hill on Tuesday. (Alex Brandon/Associated Press)

"In recent months, we have not lived up to the high standards our customers and the public have come to expect from Toyota," he said.

Lentz insisted that the sudden acceleration problem that led to the recall of millions of vehicles was not due to electronic problems, as some critics have alleged.

"Toyota all but ignored pleas from consumers to examine sudden unintended acceleration events," said Democratic Representative Bart Stupak at the outset of his remarks.

"They boast in a briefing of saving Toyota $100 million by negotiating a limited recall. They claim that they first became aware of sticking pedals in late October of 2009 when in fact they had received numerous complaints many months and years earlier."

But the most shocking moment might have been when Lentz acknowledged that the massive recall might not completely resolve acceleration problems.

The company is still investigating the issue, including whether electronics of the gas pedal system might be at fault, but the company has not found any evidence of that yet, Lentz said.

Lentz has said before that he was confident the fixes Toyota was installing for those issues would correct the problem.

Drivers speak

The first witness at the hearing was Rhonda Smith, a Tennessee woman who said her Lexus suddenly sped up to 160 km/h when she was behind the wheel in October 2008.

"I prayed for God to help me," Smith told members of the House energy and commerce subcommittee. Unable to stop the vehicle despite having two feet on the brake, she said she called her husband. "I knew he could not help me, but I wanted to hear his voice one more time," she said tearfully.

She was eventually able to turn off the engine after the car slowed down on its own. Smith told the panel she got no satisfaction from her complaints to Toyota.

The subcommittee's investigation is the first congressional hearing into the Japanese automaker's problems.

U.S. Transportation Secretary Ray LaHood will testify before the House energy and commerce committee's investigative panel on Tuesday. (Cliff Owen/Associated Press)

Committee investigators have already suggested that U.S. Transportation Secretary Ray LaHood and his agency were too slow to respond to 2,600 complaints of sudden unintended acceleration from 2000 to 2010.

LaHood denies that and argues the government had consistently pushed Toyota to correct its problems.

LaHood is scheduled to testify last.

In statements prepared for testimony before a congressional committee, LaHood says the government's investigation of Toyota includes the possibility that electronic problems had a role in sudden acceleration. The company has blamed the problem on misplaced floor mats and sticking accelerator pedals.

LaHood and Toyota's worldwide president Akio Toyoda are scheduled to testify before the committee on oversight and government reform on Wednesday, also in Washington.

On Tuesday, Japanese politicians urged Toyota executives to use the opportunity to assuage fears that Toyota vehicles are unsafe.

"Toyota is a company that has always put safety first," Trade Minister Masayuki Naoshima told reporters. "I hope its explanation will help the U.S. public understand this."

Toyota must work to rebuild its reputation with American consumers, Naoshima said. "Regaining trust is the most important thing for Toyota."

With files from The Associated Press